A type of motorcycle has been proposed which has a body height adjustor which is capable of adjusting the body height by using a front suspension and a rear cushion unit. In accordance with this body height adjustor, pressurized oil is supplied to or discharged from each one of the hydraulic jacks of the front suspension and the rear cushion unit so as to change the lengths of the front suspension and the rear cushion unit and, hence, to change the body height of the vehicle.
In accordance with this type of body height adjustor, there is a possibility of the hydraulic oil being supplied to or discharged from only one of the hydraulic jacks of the front suspension and the rear cushion unit and, hence, a possibility of non-uniformity of expansion/contraction of the front suspension and the rear cushion unit. In such an event, there is the risk that the body height balance in the longitudinal direction of the motorcycle will adversely influenced.
Another type of body height adjustor is known in which hydraulic hoses are provided for hydraulic communication between the front suspension and a body height adjusting unit and between the body height adjusting unit and a rear cushion unit. Through these hydraulic hoses, pressurized oil is supplied from the body height adjusting unit to the hydraulic jacks of the front suspension and the rear cushion unit or is discharged from the same so as to change the lengths of the front suspension and the rear cushion unit, thereby adjusting the body height of the cycle. A variation of this body height adjustor which improves the assembly performance of the motorcycle frame is possible in which two hoses detachably connected by means of a hose connector are provided in place of the hydraulic hose connecting the front suspension and the body height adjusting unit. However, if such a hose connector is disposed in front of the front suspension or at the rear of the body height adjusting unit, the hydraulic hose layout is rendered complicated.
Furthermore, because the body height adjusting unit of the above-described body height adjustor is disposed closer to the rear cushion unit, it is necessary to carefully design the layout of the hydraulic hose connecting the body height adjusting unit and the front suspension. That is, it is necessary to avoid obstruction by means of the hydraulic hose to the steering operation of the front fork.
A motorcycle upon which the above-described body height adjustor is provided is constructed so as to be able to stand stably when the side stand is set upright on the condition that the body height is set to a lower height lever. However, when the body height is set to a higher height level, there is a possibility of the rider setting the side stand upright so as to make the motorcycle stand without changing the body height from the higher height lever to the lower height level. The rider may fail to confirm whether the motorcycle body is in the higher position or lower position before setting the side stand upright, while the motorcycle body is maintained at the higher position. There is also a possibility of a phenomenon in which even if the body height adjustor is changed over by the rider so as to select the lower body height when the motorcycle is stopped and made to stand, the body height adjusting operation will be unable to be attained, so that the motorcycle stands still in the higher position. This is because, since the adjustment to the lower height is effected by means of the weight of the body, and since an initial pressure is applied to the reserve tank, the force of the weight applied to the hydraulic jacks is reduced, so that the adjustment operation is not effected, if the motorcycle body is inclined at an earlier time with the side stand extended. In such events described above, the body inclination is increases so that the standing attitude becomes unstable, and there is therefore the risk of the motorcycle falling.